Update app.py

app.py

@@ -149,7 +149,7 @@ class ChatbotAPP:
             
             firstmsg =""
             if self.isFirstRun:
-                seld.start_time = datetime.now()
+                self.start_time = datetime.now()
                 self.context = self.initContext
                 self.isFirstRun = False
                 firstmsg = prompt